This application addresses broad Challenge Area (15) Translation Science and Specific Challenge Topic, 15-AI-103* Develop drugs for neglected tropical diseases, with a special emphasis on malaria. With regard to the annual toll of people killed, malaria remains one of the deadliest diseases in the world today, as it has been so for thousands of years. For each of the 1 million people killed each year there are hundreds that are severely sickened by malaria parasites. Indeed, malaria is one of the most frequent causes of sickness and death in the world today but especially in sub-Saharan Africa where its victims are primarily young children and pregnant women. And the situation is worsening due to the emergence and spread of strains of Plasmodium parasites that harbor resistance to multiple drugs including: the quinolines - chloroquine, quinine, and mefloquine;the antifolates - pyrimethamine and sulfadoxine;and the anti-respiratory combination of atovaquone and proguanil. In some areas of the world, especially in SE Asia, multidrug resistance has forced an absolute reliance on the endoperoxide artesunate for treatment of malaria - a razor thin wall of opposition to a total collapse of therapeutic options for malaria. We have discovered a class of compounds which we refer to as "Pharmachins" with equal and potent activity against multidrug resistant strains of Plasmodium falciparum including strains harboring high level resistance to chloroquine, quinine, mefloquine, Fansidar and Malarone. Our current lead molecule, Pharmachin 128 (PH128), exhibits IC50 values in the low nanomolar range against all tested strains, e.g., D6, Dd2, 7G8 and Tm90-C2B. PH128 is active by oral means of administration in P. berghei and P. yoelii-infected mice with ED50 values of ~2.7mg/kg/day and ED90 values of ~4.6mg/kg/day in modified 4-day tests (i.e., drug administration begins with demonstration of patency). These values are strikingly similar to published reports of chloroquine's action profile in these two systems. We feel that PH128 represents an excellent lead candidate to replace chloroquine. PH128 exhibits physical, chemical and pharmacological qualities that are considered highly desirable in a new antimalarial - ease of synthesis, low cost of goods, achiral, low molecular weight (e.g., <500), log P value <5, stable salt formulation, and strong antiparasitic action in vitro and in vivo, even against multidrug resistant strains. In the proposed work we seek to dramatically accelerate the transition of our Pharmachin discoveries to advance two very strong lead candidates through a challenging array of preclinical studies designed to optimize antiparasitic activity, efficacy, metabolic stability, safety, and delivery. These studies are broadly outlined below with greater detail provided in the narrative. Specific Aims: 1. To optimize Pharmachins for antimalarial activity in vitro against multidrug resistant strains of P. falciparum and in vivo vs. two different rodent species of malaria, P. yoelii and P. berghei, 2. To evaluate Pharmachins for metabolic stability (t1/2) and fate with CYP450 reaction phenotyping in both murine and human microsomal systems and assessment of pharmacology in vivo, 3. To evaluate selected Pharmachins for potential genotoxicity in a prokaryotic system, 4. To conduct in vitro tests to assess Pharmachins for specific interactions with biogenic amine transporters/receptors and for hERG channel inhibition, 5. To conduct toxicological assessment of PH128 (and another lead candidate) in mice, and 6. To establish the propensity for Pharmachin 128 resistance in P. falciparum parasites (Dd2) in vitro. In summary, we hypothesize that Pharmachins can serve as affordable "chloroquine replacement drugs" that can be used on a worldwide scale to combat multidrug resistant malaria even in the most vulnerable populations, pregnant women and young children. Furthermore, Pharmachins represent an important component of this lab's overall commitment to developing a cocktail of chemotherapeutic agents that can be used to eradicate malaria. PUBLIC HEALTH RELEVANCE: This application addresses broad Challenge Area (15) Translation Science and Specific Challenge Topic, 15-AI-103* Develop drugs for neglected tropical diseases, with a special emphasis on malaria.